Two-way plow



June 28, 1949, R. T. EVANS ET AL Filed May 5, 1945 2 Sheets-Shana?.V l

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R. T. EVANS ET AL TWO -WAY PLOW 2 Sheets-Sheet 2 Filed May 5, 1945Patented June 28,- 1949 Two-WAY rLow Russen' r. Evans and .101m n.clasen, Anaheim,

Calif., assignors to Alice MarianV Mellen, Whittier, Calif.

Application May 5, 1945, Serial No. 592,104

17 Claims.

This invention relates to plow constructions in which two oppositelypitched plow bottoms are employed so that furrows may be turned ineither direction with respect to the direction of travel of a. vehicleby which the plow is drawn.

The generalobject of this invention is to improve two-way plowconstructions in certain interconnected plow bottoms may be selectively'raised and lowered upon actuation by the mentioned automatic liftmechanism when a plow supporting frame is raised and lowered thereby`for the purpose of bodily moving the two plows to and from plowingposition.

It is a further object of the invention to provide trip means wherebythe plow bottoms of the two-way plow may be automatically andalternately elevated by successive actuations of power lift mechanism bywhich the two-way plow is bodily lifted, such trip means beingautomatically disengaged from operative position by development of apredetermined spring-loading `created by lifting movement. It is afurther object of the invention to take advantage of the operation ofgravity as a means of initiating the tripping function when therespective plow bottom is to be elevated.

According to a preferred embodiment of the invention, thecolter-shifting device is in the form of a disk connected with thecolter support and adapted to be engaged bya beam supporting one of theplow bottoms when the respective plow bottom is being lifted, whereby toshift the colter support toward a beam supporting the other plow bottomas the latter is being lowered. The automatic means for selectivelyraising and lowering the plow bottoms includes automatic trippingmechanisms connected with jointed` levers by which the respective plowbottoms are raised into inoperative position and by which they arebraced in plowing position when lowered. These trip mechanismsrespectively include trip arms adapted to be movably mounted upon afixed portion of a draft vehicle, each trip arm being provided withengaging means adapted to releasably engage a yielding detent on alifting arm comprising one of the members of the respective jointedlever, the yielding detent being spring-controlled so as to beincreasingly spring-loaded as the lifting arm changes position, thedetent being automatically disengaged from the respective trip arm uponattainment of a predetermined maximum spring-load. Such maximumspring-load is accomplished when the respective lifting arm hasapproximately reached the limit of its elevating movement. Suchelevating movement is accomplished by bodily elevation of the structureupon which the plow bottoms are carried.

Other objects and features of the invention will be apparent to thoseskilled in the art upon reference to the following specification and tothe accompanying drawings wherein certain embodiments of the inventionare disclosed for the purpose of illustration.

In these drawings,

Fig. 1 is a perspective View of a two-way plow embodying the features ofthe present invention, its general relationship to a tractor employingpower lift mechanism being indicated in broken lines;

Fig. 2 is a side elevation corresponding with the perspective view ofFig. 1, the relation of the twoway plow construction and its automaticshift mechanism to a hydraulic power lift on the tractor beingillustrated in greater detail;

Fig. 3 is a front elevation, taken approximately from the line 3--3 ofFig. 2, portions of the trip mechanism and the elevated plow beingomitted for the purpose of clarity;

Fig. 4 is a detail, partly in front elevation and partly in verticalsection, indicated approximately by the line 4-4 of Fig. 2;

Fig. 5 is a detailed plan view, taken from the line 5-5 of Fig. 4;

Fig. 6 is a detail of mounting and adjusting means for a plow beam,taken on the lines 6--6 of Fig. 2; and

Figs. '7, 8 and 9 are fragmentary elevations indicating relativepositions of the trip mechanism at different stages of actuation, Fig.'I indicating the initial lifting relationship between a lifting arm andits trip arm, Fig. 8 indicating the nal or kick off position of suchtrip arm at the end of the lifting operation, and Fig. 9 indicating thenon-engaging and non-lifting relationship between the trip arm andlifting arm of a previously elevated plow bottom.

In the drawings the rear housing I5 of a tractor is represented inbroken lines. To the opposite sides of the housing I5 two elevator armsi8 are pivoted at I9. The rearward ends of the arms I8 serve to supportthe lower end of an A-frame 20 whose upper end has connected thereto:as: by means of a bolt 2l a positioning arm 22, the forward end ofwhich is connected with the tractor housing I5 through the medium of apart 23 which may be an automatic control conventionally employed onsome tractors for adjustment of the A-frame 20 or similar framework inaccordance with the pull or thrust imparted to the positioning arm 22through the A-frame 20. The elevator arms I8 are controlled by means ofelevator links 24 whose lower ends are connected respectively tointermediate portions of the arms I8 and whose upper ends are connectedto the outer ends of a forked bell crank 25 pivoted on the housing I5 asby means of a rock shaft 26, an upper arm 21 of the bell crank 25 beingconnected with a hysubstantially the fun length of the plate 4o. The

bolts 53 bind the adjacent end of the plate 54 agalnstthe plate 48. \A\tits forward end the binding plate 54 is apertuxed to receive the bolts45 and 48 by which the forward portion ofthe plate 54 is bound to theforward portion of plate 48.

of the bolts 45 and 48 takes place in the slot 46 in the forward end ofthe respective bearing draulic lift mechanism 28 under the control ofthe operator of the tractor.

The A-frame comprises two bent side mem- Lyeniently retained as by nuts32 and cotter keys 32a. The shaft 3| at the lower end of the A- frame 20carries a pair of plow beams 33 in the form of I-beams whose lower endsare curved downward and support conventional plow bottoms 34 which, forconvenience, are hereinafter called plows and which include the usualmold boards 35 and landsides 36, the plow as a whole being in eachinstance secured to its I-beam 33 by any appropriate attaching means 31.

The forward portion of each of the plow beams 33 is adjustably mountedupon the transverse shaft 3| through the medium of ra bearing plateprovided with side fianges 42 whose forward ends are notched and weldedat 43 to a corresponding sleeve 44 carried upon the shaft 3l. Theunderside of each beam 33 is bound upon the' top face of its bearingplate 40 through the medium of a, series of bolts. One bolt 45 extendsvertically through a corresponding bore inthe end of the beam 33 andthrough a slot 46 in the plate 4l), the tightening of this bolt 45serving in part to retain the adjustment of the respective beam. Inorder to provide for a limited amount of lateral tilt of each beam 33, alug 41 is welded to the outer side of the beam and this lug has a bolt48 passed therethrough and also through the slot 46 in the plate 40. Theslot 46 permits lateral adjustment of the beam 33 .by loosening andsliding the bolts 45 and 48 therealong.` In addition to such retainingnuts 49 as may be required at the ends of each bolt 48, nuts 50 areprovided on intermediate portions of the respective bolt 48 and arebound against adjacent faces of the lug 41 and the plate 40 to act aspositioning means for retaining the lug 41 in its properly tiltedposition with respect '65 plate 40, and adjustment of the nuts 48 and5|) on the bolt 48 with respect to the lug 41 provides such tip o f thebeam 33 as may be required.

For the purpose of lowering one of the plows 34 simultaneously with theraising of the other plow,

a cable 60 is passed through a pulley 6I carried in a clevis 62 securedto a spacing sleeve 63 and supported by a cross-bolt 64 between theupper ends of the frame members 38. The ends of the cable 60 are securedby means of clamps 65 in eyes 66 fixed on the ends of bolts 61 carriedby the beams 33 adjacent the upper ends of the curved portions whichcarry the plows 34. Adjustment of the length of the cable 60 ispermitted by the clamps 65. Also, if desired to lower both plows 34 sothat they may be used together for the purpose of ditching, the pulley6I and the clevis 62 may be disconnected by removing the bolt 64, or thecable 60 may be disconnected from the pulley 6I by removing one of theclamps 65.

Means is provided for raising each of the plows 34,this means comprisinga jointed lever 68 for each plow. Each lever comprises a lifting arm 10which is connected by a pivot 12 to a link section 13 comprising twospaced links between the corresponding ends of which the lifting arm 10is disposed. When a plow 34 is in plowing position, its jointed lever 68assumes the straightened position illustrated in both Figs. 1 and 2, andin this position the respective lever 68 serves as a brace by reason ofthe fact that the lower end of the lifting arm 10 is moved slightly pastits dead center position and engages a stop bar 14 welded to theunderside of the links 13 and spanning the space between them. The lowerends of the links of each link section 13 are pivotally mounted by apivot bolt 15 upon opposite sides of an ear 16 of a slidable bracket 11carried on the rearward portion of the respective plow beam 33 andretained` by the respective bolt 61 to which the flexible cable 60 isattached. The ear 16 maintains the properly spaced relationship of thetwo members of each link 13. For the purpose of adjustment to controlthe suck of each plow, that is, its penetration into the soil, eachbracket 11 is adjustable along the respective plow beam 33 to any one ofa series of positions represented by a series of openings or slots 18 inwhich the respective bolt 61 may be selectively placed in accordancewith the amount 'of lowering to be permitted by the respective lever 68.

The upper or forward end of each lifting arm 10 is pivoted upon theupper portions of the A-frame 20 by means of across-pivot bolt 88 whichpasses through upper portions of the frame members 30, the lifting arms10 andthe frame members 30 being maintained in properly spacedrelationship by short spacing sleeves 8|.

armaniV The extremity of each lifting arm' 10 beyond the pivot bolt 80is provided with a trip cam or latch 82 adapted to cooperate with acorresponding trip arm 84 for actuating the respective lifting arm undercertain conditions. Each trip arm 84 is supported by means of a pivot'bolt 85 rupon a bracket 86 secured to a rear portion of the housing l5of the tractor. The trip arms 84, which extend upward from the pivots85, are so arranged that their free upper ends lean rearward under,

the influence of gravity whereby to maintain their rear edges inengagement with the forward end of the latches 82. In this manner theforward end of each latch 82 may travel in a path to engage a shoulder88 provided at the top of a tapering notch 80 cut into the rear edge ofthe respective trip arm 84. To guard against possible displacement ofthe respective trip arms 84 from the indicated operative position,appropriate retaining loops 92 of a sufciently rigid material aresecured to the extremities of the lifting arms 10. Thus, as the triparm's 84 move within their loops 92, and as the A-frame 20 is raised andlowered, the arms 84 swing toward and awayl from the lifting arms 10.

The trip cam or latch 82 of each of the lifting arms 10 is in the formof a leaf whose forward end is wrapped around a stud pin 94 secured tothe adjacent side of the end of the respective lifting arm l0, which endof the lever arm 10 is indicated at 10a and is offset upwardly for thepurpose of avoiding contact with the underlying portion of therespective frame member 30 when the respective lifting arm is inplow-elevating position. The rearward extremity of the latch 82 hassecured thereto one end of a tension spring 95 whose opposite end issecured to the lifting arm 10. The spring 95 is adapted to be tensionedby movement of the latch 82 `under actuating iniiuence of the respectivetrip arm 84 whereby the corresponding shoulder 88 may maintain itsengagement with the latch 82 until such time as the spring 95 istensioned sufliciently during movement of the parts to the position ofFig. 8 to jerk the latch 82 for dislodgment of the shoulder 88. Whensuch dislodgment occurs, the retaining loop 92 prevents throw of therespective trip arm 84 to an inoperative position. Meanwhile, as theother plow 34 descends and causes the end 10a of the respective arm 10to rise, the angular position of the respective latch 82, which positioncorresponda somewhat with the broken line position of Fig. 8, preventsoperative engagement of the latch 82 by the respective shoulder 88through deflection of such shoulder 88 so that such latch 82 may slidepast its shoulder 88 and continue to rise.

It is at times desirable to move the lifting arm l0 manually, and forthis purpose, each arm 'l0 has a laterally offset extension 96 attachedthereto by bolts 91, the extremities of these extensions 96 being withinthe reach of the operator of the tractor and adapted to be depressed orelevated by him.

The present two-way plow .construction is desirably provided with anauxiliary earth-cutting tool in the form of a trailing colter disk |00which is carried on an axle |02 supported in a fork |03 secured as bywelding to the lower end of a bracket |04 which is inserted into thelower end of a hollow supporting post |05 and secured therein as by aset screw |06. The upper end of the post |05 is mounted on a pivot boltl0? supported in lugs |08 welded to an upper sloping portion of one ofthe members 30 of the A-fram'e 6 20. The colter disk |00 is adapted tobe aligned approximately with the forward point of an operating plow 34and to be shifted into alignment with the point of the other plow whenthe latter is lowered into operating position. For this purpose, thelower portion of the post |05, which lies forward of the shaft 3|, isadapted to be shifted along the shaft 3|, the positioning of thisportion of the post 05 being accomplished by an angle plate ||0 which iswelded to the`post |05 and overlies the shaft 3|, a portion I |0adepending on the side of the shaft 3| opposite from the post |05,

i that is, on the rear side of the shaft 3|. To the upper face of theangle plate H0, there is welded an angularlyI disposed upwardlyextending stud post i |2. Rotatably carried upon a reduced upper end ofthe stud post ||2 is a shifting disk ||4, which acts as a cam, the disk||4 being retained asbyanutll.

As illustrated in Figs. 4 and 5, the portion of each bearing plate 40carrying the respective plow beam 33 projects somewhat beyond thecorresponding plow beam 33. Advantage is taken of this spacing and theinset position of the web of the I-beam forming the beam 33 forautomatic shifting of the colter disk |00.

The shifting disk ||4 serves as a means by which to move the lower endof the post |05 laterally from side to side and thereby also shift thecolter disk |00 accordingly, the shifting action being accomplishedthrough the medium' of the adjacent edges of the bearing plates 40 andadjacent sides of the I-beams 33. As illustrated in Figs. 4 and 5, theinner edges of the bearing plates 40 extend inwardly somewhat from theadjacent sides of the beams 33 so that rising and falling movements ofthe beams 33 and their plows 34 cause the edges of the plates 40 toengage the shifting disk ||4 to move it laterally, together with thelower end of the post |05. Thus, as one beam 33 is elevated, theadjacent edge of the corresponding plate 40 engages the disk ||4andmoves it toward the web of the opposite I-beam 33 which meanwhile hasbeen lowered so that its plate 40 clears the disk ||4 and permits thelatter to be moved into engagement with the web of the respectiveI-beam. In this manner, as one plow 34 and its I-beam' 33 and bearingplate 40 are elevated, that plate 40 moves the shifting disk ||4,thereby shifting the lower end of the post |05 and the colter disk |00so that the latter is aligned approximately with the point of the plow34 which is being lowered, engagement of the shifting disk ||4 with theedge of the bearing plate 48 which is being lowered serving as a stopfor the colter-shifting movement.

Operation justed by means of one of the clamps 65. Whenthe plow andtractor reach plowing position in the eld, the A-frame 20, togetherwitlrthe plows 34, is bodily lowered through the medium of the elevatorarms |8 by actuation of the hydraulic lift mechanism 28 under control ofthe along the rear edges of the trip arms 84.

amarsi tractor operator. Under these conditions, one

of the plows 34 will be placed in plowing `posi-- tion with the colterdisk |88 in alignment with the point thereof, the other plow 34 beingelevated. This relative position of the plows 34 is illustrated in Figs.1 and 2, where the lowered plow 34 is braced by its jointed lever 68 andthe other jointed leverf68 is in its collapsed lifting position, thecable 88 serving to hold the elevated plow 34 in elevated position withits weight counterbalanced by the lowered plow. Forward movement of thetractor causes a furrow to be thrown by the lowered plow.

When the tractor reaches the edge of the field' and pullingV the loweredplow out of the soil.

As this elevation of the A-frame 28 occurs, the forward rolled edges ofthe latches 82 ride up When about three-fourths of the total elevationof A-frame 28 has taken place, the forward edge of the latch 82 on thelifting arm 18 of the lowered plow engages under the shoulder 88provided by the notch 88 in the respective trip arm 84. The shoulder 88is of such shape and length with respect to the shape and size of theforward end of the latch 82 and with respect to the center of the studpin 94, as indicated in Fig. '7, that the point of the shoulder`88engages the latch 182 so as to check the upward movement of the latch 82and hence to check upward movement of the end 18a of the correspondinglifting arm 18.

As the lifting movement of the respective lifting arm 'I8 is commencedby the restraining iniluence of the respective trip arm 84, the bite ofthe point of the corresponding shoulder 88 tends to restrain rockingmovement of the latch .82 upon its stud pin 94, thereby tending toretain the original relationship between the respective trip arm 84 andlatch 82 during the time when the corresponding lifting arm 18 and itsend 18a are being moved into the elevated position illustrated in Fig.8. As the angle of the lifting arm 18 is changed with respect to thetrip arm 84, the latch 82 being held against substantial change inposition, the spring 95 is correspondingly tensioned, as indicated inFig. 8, this tension steadily increasing until such a time that thetension of the spring 95 together with a limited amount of change inangular position of the latch 82 causes the latch 82 to be jerked intoits original position with respect to its arm 18, such actiondisengaging the respective trip arm 84 and throwing it back against theretaining loop 92. This kick-out action occurs when the elevation of theA-frame 28 is substantially complete, a limited amount of :additionalA-frame movement being permitted by reason of the fact that the shoulder88 in the resultant relative position will not accomplish liftingcontact with the latch 82. By action of the cable 68, the previouslyelevated plow 34 will be lowered slowly in counterbalancedrelationship`with the plow 34 which has just been elevated. As thisdescending plow 34 moves downwardl and the end 18a of the respectivelifting arm 18 moves upward during elevation of the A-frame 28, thesharper angular relationship of the respective latch 82, which will liealong the axis `of its lifting arm 18, will be such with respect to theshoulder 88 on the corresponding trip arm 84 that such shoulder 88 willbe denected and snee off the forward end of the latch 82 and notaccomplish a restraining and lifting engagement therewith. This lasteffect is indicated in Fig. 9.

/ Upon downward movement of the A-frame 28 to return it to operativeposition, the forward ends of both ofthe lifting arms 18 slide down therear edges of the respective trip arms 84, the end ofthe arm 18 furthelowered plow riding down over the respective shoulder 88 and notch 98 tothe initial position, as seen in Figs. 1 and 2,

the depressed end of-the lifting arm 18 of the elevated plow lying at alower position with respect to its shoulder 88 and notch 98 under theseconditions. The parts are thus restored to the normal positionillustrated in Figs. 1 and 2, with the difference that the positions ofthe plow 34 have .been reversed. Upon a subsequent upward excursion ofthe A-frame 28, the same operation of the parts as above-described takesplace with the result that the relative positions of the plows 34 areagain reversed. In this manner a field being plowed may be traversedback and forth, the furrows being thrown always in the same direction.

When desired to use the implement as a ditcher, the cable 88 may bedisconnected by removal of one of the clamps 65, and both plows lowered.In order to avoid lifting of the plows 34 by the trip arms 84 when theA-frame 28 is being elevated for bodily upward movement of the entireplow structure, the trip arms 84 are held out of operative engagementwith the latches 82 in any desired manner.

As the respective plow beams 33 and their bearing plates 40 rise andfall, the inner edges of the plates 48 drive the shifting cam disk H4whereby to shift the lower end of the colter-supporting post |85 andmove the colter disk |88 into alignment with the lowered plow.

Since many variations of the improvements l herein disclosed will becomeapparent to those skilled in the art, it is intended to cover suchmodifications as fall within the scope of the appended claims.

We claim as our invention:

1. n combination in a plowing structure; a frame; means to lift saidframe; a plow movably carried on said frame; a lifting arm for said plowconnected with said plow and movably mounted on said frame; trip meanshaving a shoulder with respect to which said frame is movable; movablelatch means on said arm comprising a leaf member one end of which isadapted to engage with said shoulder of said trip means; and tensionablemeans controlling said latch means and connected with the other end cfsaid leaf member and adapted to jerk said leaf member into position todisengage the latter from said trip means upon development ofpredetermined tension in said tensionable means.

2. In combination in a two-way plow structure: a frame; a pair ofoppositely pitched plows movably carried by said frame andinterconnected to be selectively and simultaneously respectively loweredand raised to and from operative positions; means to move said frame;lifting means for each of said plows supported on said frame andrespectively connected with said plows; trip means associated with eachof said lifting means and adapted to actuate said lifting means to raiseand lower the respective plows selectively; relatively mcvable tensionedmeans connected with each of said lifting means and adapted forengagement with the respective trip means to cause and tensioning springmeans for each lifting `means connected with said tensioned means andadapted to be tensionedy by actuation of said lifting means to push therespective trip means away from said tensioned means upon development ofpredetermined tension in said tensioning spring means.

Y 3. A combination according to claim 2 including means to move saidframe vertically whereby to actuate a lifting means engaged with itsspective trip means.

4. In combination in a two-wayplow: a frame; a pair of oppositelypitched plows movably mounted on said frame and interconnected, wherebyone plow is simultaneously lowered as the other is raised; lifting armsrespectively connected with said plows and pivoted upon said frame toraise said plows selectively upon said frame; means to lift said frameand plows bodily; trips retained against substantial movement in 4thedirection of lift of said frame and adapted to engage and actuate saidlifting arms respectively upon lift of said frame, said trips beingadapted to swing to engage and disengage saidarms; means under tensionto kick said trips respectively out of engagement with said liftingparmsupon attainment of a predetermined relation between said arms and saidtrips; and means lto produce and increase said tension as saidpredetermined relation is approached.

5. A combination as in claim 4 wherein said trips are upstanding triparms having notches providing shoulders on their rear edges, and saidmeans under tension are latch means carried respectively by said liftingarms in position to en gage under said shoulders.

6. A combination as in claim 4 wherein said trips are upstanding triparms having notches `providing shoulders on upstanding edges thereof tocooperate with said means under tension, said means under tension beinglatch means carried respectively by said lifting arms in position toengage under said shoulders in one angular position of said arms and toshift said shoulders from such engagement in another angular position ofsaid arms.

7. A combination as in claim 4 wherein said trips are upstanding triparms having notches providing shoulders on their rear edges, and saidmeans under tension are latch means carried respectively by said liftingarms in position to engage under said shoulders, said means to increasesaid tension being springs connected with `said latch means to beincreasingly tensioned by pressure of said shoulders on said latch meansas said frame is lifted. Y

8. A combination as in claim 4 wherein said means under tensioncomprises a movable cam for each lifting arm, each arm being adapted tobe so positioned when a plow is being lowered as to avoid liftingengagement of the respective trip with the respective lifting arm.

9. In combination in a two-way plow: a frame to be lifted bodily; a pairof oppositely pitched plows movably mounted on said frame to be liftedtherewith and interconnected whereby one plow is simultaneously loweredas the other is raised;

vlifting arms respectively connected wiith said plows and pivoted uponsaid framel to raise said plows selectively upon said frame; trip meansdisposed in substantially upright position and adapted to engage andactuate said lifting arms respectively upon lift of said frame, saidtrip 10 means being movable toward and away from said lifting arms;tensioned yielding means presenting lifting and deflecting surface meanspositioned to so that saidl trip means engage said tensioned` means toactuate said arms as said arms are lifted by said frame, andwherein saidtensioned means are disposed at a relatively sharp angle with respect to-said trip means when said arms and trip means are in asecondpredetermined angular relationship so that said tensioned means displacesaid trip means from arm-engaging position. t' y.

11. A combination as in' claim 10 wherein said tensioned means yieldvto`retain engagement of.4

said t'rip means with saidjarms while initially in said one` angularrelationhip, the tensionpfy i said'tensioningmeans incr' sing assaidt'en`v sioned' means yieldto' dis ace said trip'meansfrom'engagement iifiths'a'illarms as a third pre.. determined angularrelationship is attained.

12. Incombination in a twofway plow: a. frame adapted to be liftedbodily; oppositely pitched plow means movably mountednn said frame to belifted bodily therewith and interconnected whereby one plow means islowered ...simultaneously with the raising of the other plow means; apair` of lifting arm members respectively connected with said plow meansand pivoted upon said frame to raise said plow means selectively uponsaid frame; a pair of trip members adapted to beimounted againstsubstantial movement in the direction of lift of said frame andpositioned to engage and actuate said `lifting arm members respectivelyand selectively upon lift of said frame and to move to and`froinposition for lifting connection with said lifting arm members, parts ofone of said pairs of members having engaging means including tensioneddeflecting surface means, and parts of the other of saidpairs of membershaving cooperating engaging' means adapted and positioned fordeflection,

14. In combination in a two-Way plow: a4

frame; a pair of oppositely pitched plows movably mounted on said frameand interconnected, whereby one plow is simultaneously lowered as theother is raised; lifting arms respectively connected with said plows andpivoted upon said frame to raise said plows selectively upon said frame;means to lift said frame and plows bodily; trip means adapted to engageand actuatesaid 1l lifting arms respectively upon lift of said frame,said trip means being movable to and from arm engaging position; and cammeans for each` liftingv arm and adapted for engagement with theladapted to assume a position such that it will be engaged by therespective trip means to lift the respective plow as said frame is'againraised.

15. A combination as in claim k14 including tensioning means for eachcam means to provide for limited yielding movement of such cam meansupon engagement by said trip means.

16. A combination as in claim 15 wherein said tensioning means includesresilient means whose tension increases with increasing relativemovement of said cam means with respect to said trip means, whereby todislodge the respective trip means as a predetermined position of saidframe is reached.

17. A combination as in claim 14 wherein each cam means and its arm aremovable on said frame to assume a different angular relationship withrespect to their trip means as said frame approaches the limit of itslift, whereby such trip means becomes disengaged from the respective cammeans by reason of the change in angularity.

RUSSELL T. EVANS.

JOHN H. CLASEN.

REFERENCES CITED The following referenices are of record in the file ofthis patent:

UNITED STATES PATENTS Mellen et al. June 11, 1946

